import java.util.Deque;
import java.util.LinkedList;
import java.util.Queue;

public class BinaryTree {
    static class TreeNode {
        public char val;
        public TreeNode left;//左孩子的引用
        public TreeNode right;//右孩子的引用

        public TreeNode(char val) {
            this.val = val;
        }
    }


    /**
     * 创建一棵二叉树 返回这棵树的根节点
     *
     * @return
     */
    public TreeNode createTree() {
        TreeNode a=new TreeNode('A');
        TreeNode b=new TreeNode('B');
        TreeNode c=new TreeNode('C');
        TreeNode d=new TreeNode('D');
        TreeNode e=new TreeNode('E');
        TreeNode f=new TreeNode('F');
        TreeNode g=new TreeNode('G');

        a.left=b;a.right=c;
        b.left=d;b.right=e;
        c.left=null;c.right=g;
        d.left=null;d.right=null;
        e.left=f;e.right=null;
        f.left=null;f.right=null;
        g.left=null;g.right=null;

        return  a;
    }

    // 前序遍历
    public void preOrder(TreeNode root) {
        if(root==null){
            return;
        }
        System.out.print(root.val);
        preOrder(root.left);
        preOrder(root.right);
    }

    // 中序遍历
    void inOrder(TreeNode root) {
        if (root == null) {
            return;
        }

        inOrder(root.left);
        System.out.print(root.val);
        inOrder(root.right);
    }

    // 后序遍历
    void postOrder(TreeNode root) {
        if (root == null) {
            return;
        }

        postOrder(root.left);
        postOrder(root.right);
        System.out.print(root.val);
    }

    public static int nodeSize;

    /**
     * 获取树中节点的个数：遍历思路
     */
    void size(TreeNode root) {
        if(root==null){
            return ;
        }
        nodeSize++;
        size(root.left);
        size(root.right);
    }

    /**
     * 获取节点的个数：子问题的思路
     *
     * @param root
     * @return
     */
    int size2(TreeNode root) {
        if(root==null) {
            return 0;
        }
        return size2(root.left)+size2(root.right)+1;
    }


    /*
     获取叶子节点的个数：遍历思路
     */
    public static int leafSize = 0;

    void getLeafNodeCount1(TreeNode root) {
        if(root==null){
            return;
        }
        if(root.left==null&&root.right==null){
            leafSize++;
        }
        getLeafNodeCount1(root.left);
        getLeafNodeCount1(root.right);
    }

    /*
     获取叶子节点的个数：子问题
     */
    int getLeafNodeCount2(TreeNode root) {
        if (root==null){
            return 0;
        }
        if(root.left==null&&root.right==null){
            return 1;
        }
        return getLeafNodeCount2(root.left)+getLeafNodeCount2(root.right);
    }

    /*
    获取第K层节点的个数
     */
    int getKLevelNodeCount(TreeNode root, int k) {
        if(root==null){
            return 0;
        }
        if(k==1){
            return 1;
        }
        return getKLevelNodeCount(root.left,k-1)+getKLevelNodeCount(root.right, k-1);
    }

    /*
     获取二叉树的高度
     时间复杂度：O(N)
     */
    int getHeight(TreeNode root) {
        if(root==null){
            return 0;
        }
        int leftHeight=getHeight(root.left);
        int rightHeight=getHeight(root.right);
        return leftHeight>rightHeight?leftHeight+1:rightHeight+1;

    }


    // 检测值为value的元素是否存在
    TreeNode find(TreeNode root, char val) {
        if(root==null){
            return null;
        }
       if(root.val==val){
           return root;
       }
       TreeNode left=find(root.left,val);
       if(left!=null){
           return left;
       }
       TreeNode right=find(root.right, val);
       if(right!=null){
           return right;
       }
        return null;
    }

    //层序遍历
    void levelOrder(TreeNode root) {
        if(root ==null){
            return;
        }
        Queue<TreeNode> queue=new LinkedList<>();
        queue.offer(root);
        while(!queue.isEmpty()){
            TreeNode node=queue.poll();
            System.out.print(node.val);
            if(node.left!=null){
                queue.offer(node.left);
            }
            if(node.right!=null){
                queue.offer(node.right);
            }
        }
    }


    // 判断一棵树是不是完全二叉树
    boolean isCompleteTree(TreeNode root) {
        if(root==null){
            return true;
        }

        Queue<TreeNode> queue=new LinkedList<>();
        queue.offer(root);
        while(true){
            TreeNode node=queue.poll();
            if(node!=null) {
                queue.offer(node.left);
                queue.offer(node.right);
            }else{
                break;
            }
        }
        while(!queue.isEmpty()){
            TreeNode node=queue.poll();
            if(node!=null){
                return false;
            }
        }
        return true;
    }

    public static void main(String[] args) {
        BinaryTree binaryTree=new BinaryTree();
        TreeNode root=binaryTree.createTree();
        binaryTree.preOrder(root);
        System.out.println();
        binaryTree.inOrder(root);
        System.out.println();
        binaryTree.postOrder(root);
        System.out.println();
        binaryTree.size(root);
        System.out.println(nodeSize);
        System.out.println(binaryTree.size2(root));
        System.out.println(binaryTree.getKLevelNodeCount(root,2));
        System.out.println( binaryTree.getHeight(root));
        binaryTree.getLeafNodeCount1(root);
        System.out.println(leafSize);
        System.out.println(binaryTree.getLeafNodeCount2(root));
        System.out.println(binaryTree.isCompleteTree(root));


    }
}
